More trouble burning NASA’s lunar rocket

NASA made a third attempt to burn its new Space Launch System lunar rocket during a test countdown on Thursday, but once again, a series of technical problems triggered several delays, preventing engineers from pumping 730,000 gallons of liquid hydrogen and oxygen into the booster’s huge first phase as planned.

Problems with a helium pressure valve in the upper stage of the SLS rocket, discovered during a fuel test last week, limited Thursday’s attempt to refuel to the core stage alone, but engineers were only able to fill its hydrogen tank to the 5% level and oxygen level tank to about 49%.

This is due to problems with a gaseous nitrogen supply line, oxygen temperature violations under initial load, an unexpected “pressure rise” when the liquid hydrogen stream is switched to high speed, and indications of a hydrogen leak in a launch pad when trying to resume “rapid filling” after a stop.

The Space Launch System lunar rocket on Thursday stops 39B at the Kennedy Space Center. / Credit: CBS News

Two scheduled terminal countdown “runs” were scheduled to take the count all the way to T-minus 33 seconds and then, after a reuse, down to T-minus 9.3 seconds to verify fuel handling and launch day procedures. But the countdown was never resumed after one last built-in team.

Despite the importance of the test, NASA has refused to comment on real-time launch controls due to concerns that export control laws could be violated if technical information is released before it can be reviewed. Instead, the agency uses social media – tweets and blog posts – to update journalists and the public.

The helium valve problem that prevented top-step refueling could not be repaired at the launch pad, and it is not yet known whether NASA will attempt a fourth-phase fuel test or choose to withdraw the rocket to the Kennedy Space Center’s iconic vehicle building for repair.

At that point, the agency could roll it back to the cushion for another fuel test or push on for launch. Or both. NASA executives have declined to outline even preliminary plans beyond the now-delayed fuel test, saying they want that data in hand before making any decisions on how to proceed.

The Space Launch System rocket is the most powerful launch vehicle ever built for NASA, a key element of the agency’s Artemis program to send astronauts back to the moon. With the “mega rocket” years delayed and billions over budget, NASA plans to launch an un piloted Orion crew capsule beyond the moon and back during a virgin test flight this summer.

The countdown to the dress rehearsal and fuel drill is a critical milestone on the road to launch, allowing executives and engineers to put complex ground systems and the SLS rocket through their pace under launch conditions for the first time.

Problems are not unexpected given the huge amounts of super-cold cryogenic propellants involved and the intricate systems needed to handle them safely. A scheduled six-day countdown test for the first Apollo Saturn 5 lunar rocket took 17 days to complete. Surprisingly, the SLS dress rehearsal now seems to be taking even longer.

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